The present invention relates to highly heat-resistant silicone compositions that exhibit excellent release and lubrication properties.
Diorganopolysiloxane oils possess an excellent heat resistance and excellent release properties, and for this reason have heretofore been widely used as mold-release agents in the molding of thermoplastic resins, thermosetting resins, and rubbers and as release agents for toners used in electrostatic copiers. However, the application of diorganopolysiloxane oils as mold-release agents is not without its problems. Thus, dimethylpolysiloxane oils, which are typical of the diorganopolysiloxane oils under consideration, undergo a gradual thermal decomposition in this application when the temperature of the mold surface reaches approximately 150.degree. C., and undergo a relatively rapid thermal decomposition when the mold surface temperature reaches 200.degree. C. or more. This decomposition yields a sticky gel. The accumulation of this gel during the long-term use of dimethylpolysiloxane oil as a mold-release agent can prevent the fabrication of moldings with smooth surfaces, and the production of this gel is fatal when a mirror-like smoothness is required of the molding surface. Thermal decomposition is also a problem with the use of dimethylpolysiloxane oil as a toner release agent in high-speed xerographic copiers since the hot rolls in these machines are used at temperatures around 200.degree. C. Moreover, the contemporary trend is toward substantially higher mold temperatures in pursuit of more productive molding operations and substantially higher hot roll temperatures in copiers in pursuit of shorter copy times. This has led to demand for release agents with even greater thermal stabilities. One such release agent has been proposed by Japanese Patent Application Laid Open No. 3-227206 (227,206/91), which teaches an amino-functional diorganopolysiloxane oil that has an amino equivalent weight in the range of 10,000 to 100,000.
When heated, however, amino-functional diorganopolysiloxane oils of this type will emit an ammonia odor or will discolor, and it may also gel when subjected to long-term heating. As a result, its performance as a high-temperature release agent or lubricant is not entirely satisfactory.